1. Field of the Invention
The present invention relates to a wireless power feeder for feeding power by wireless and a wireless power transmission system.
2. Description of Related Art
A wireless power feeding technique of feeding power without use of a power cord is now attracting attention. The current wireless power feeding technique is roughly divided into three: (A) type utilizing electromagnetic induction; (B) type utilizing radio wave; and (C) type utilizing resonance phenomenon of a magnetic field. The type (C) utilizing the magnetic field resonance phenomenon is a comparatively new technique and is hereinafter referred to as “magnetic field resonance type”.
The magnetic field resonance type is based on a theory published by Massachusetts Institute of Technology in 2006 (refer to Patent Document 1). In the magnetic field resonance type, a feeding coil and a receiving coil are disposed so as to face each other, and power is fed from the feeding coil to receiving coil by wireless. When the feeding coil and receiving coil magnetically resonate, high current flows in the receiving coil. By utilizing the magnetic field resonance phenomenon, high power transmission efficiency can be achieved even when the distance between the feeding coil and receiving coil is large.
In addition to the magnetic field resonance type, wireless power feeding of a type utilizing an electric field resonance phenomenon is proposed (refer to Patent Document 8). One of two electrodes constituting a capacitor is used as a feeding electrode, and the other one thereof is used as a receiving electrode. When the feeding electrode and receiving electrode are made to electrically resonate, that is, the capacitor is made to resonate, power can be fed by wireless from the feeding electrode to receiving electrode with high efficiency. Such a type is referred to as “electric field resonance type”.